Apparatus for measuring the strip flatness

ABSTRACT

The present invention provides an apparatus for measuring flatness of a hot rolled strip based on a contact load of the hot rolled strip to split rolls of a looper in the hot rolling process. The split rolls are assembled in a bracket such that each split roll can be separated from the bracket. A normal-movement control unit for moving the split rolls in the normal direction, and a tangent-movement control unit for moving the split rolls in the tangent direction are porvided at a side of the bracket bearing the split rolls. An impact absorption unit is mounted at a support that is movably connected to the tangent-movement control unit. A pre-pressure application unit is provided at the support to prevent a sensor cap and a load sensor from being released. A heat-shielding ring surrounds the load sensor to prevent the load sensor from being overheated.

This application is a 35 USC 371 of PCT/KR00/00771 filed Jul. 15, 2000.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an apparatus for measuring flatness ofhot rolled strips in a rolling mill and, more particularly, to acontact-typed strip flatness measuring device which protects loadsensors from heat or impact while controlling surface points of splitrolls to move up and down.

(b) Description of the Related Art

Generally, metal strips produced through hot-rolling slabs should bekept to be even in flatness along the width thereof.

An automatic shape controller based on a shapemeter has been frequentlyemployed for use in controlling the strip flatness during the hotrolling process. FIG. 1 illustrates a rolling mill with such anautomatic shape controller. In the automatic shape controller, ashapemeter 1 measures the shape change in the target hot rolled strip Sthrough generating laser, and detects the strip flatness based on themeasured shape change. The detected value of the strip flatness is inputinto a calculator 4 that calculates a control value. Then, dependingupon the control value, a bender controlling unit 5 controls pressure ofa bender 2 installed at the last stand, thereby controlling the stripflatness.

However, in the above strip flatness control technique, the stripflatness is basically controlled by taking the shape change of the hotrolled strip S as a criterion, and such a shape change largely differsfrom the practical value of strip flatness. Therefore, in such atechnique, the strip flatness cannot be measured in a correct manner.Furthermore, when the frontal end portion of the hot rolled strip Stransported over a roller table 3 is coiled around a coiler 6, the hotrolled strip S is flattened under strain due to the difference inrelative speeds between the last stand B and the coiler 6. Accordingly,the shapemeter 1 cannot measure the strip flatness after the hot rolledstrip S is coiled around the coiler 6.

In order to solve such problems, a contact-type strip flatness measuringdevice has been suggested. In the device, the strip flatness is measuredthrough detecting reduction in the hot rolled strip while directlycontacting it.

Split looper rolles are arranged along the width of the hot rolled stripS, and a load sensor is attached to each split roll to detect loaddistribution of the hot rolled strip S. The detected load distributionis converted to a value of strip flatness, and makes feedback to aflatness control system, thereby controlling flatness across the hotrolled strip S.

When the load distribution signal issued from the strip flatnessmeasuring device makes feedback to the flatness control system on line,uniform flatness can be obtained over the entire length of the hotrolled strip S.

However, such a contact-type load distribution measuring device shouldperform its intrinsic functions in poor working conditions such as hightemperature, high humidity, and high vibration. Furthermore, it shouldensure sufficient device stability and reliability, and detect the loaddistribution in a stable manner.

FIG. 2 illustrates a contact-type strip flatness measuring deviceinstalled at the Hoesch steel mill of German (Herman J. Kopineck,“Rolling of hot strips with controlled Tension and Flatness,” Hot stripprofile and flatness seminar, Nov. 2-3, 1988, Pittsburg Pa.). As shownin FIG. 2, a load sensor 12 is provided at an end portion of a support11 bearing a split roll 10 to detect the load applied to the split roll10, thereby measuring the strip flatness.

However, in such a device, since the difference in the maximum loads attension and compression (hereinafter referred to as the “peak load”) isso great that the load sensor 12 is liable to be broken at repeatedsensing operations, resulting in lowered precision and reduced devicelife span.

FIG. 3 illustrates another contact-type measuring device disclosed byGeorge. F. Kelk in “New developments improve hot strip:Shapemeter-Looper and Shape Actimeter”, Iron and Steel Eng., August,1986, pp. 48-56. As shown in FIG. 3, a compression-type load sensor 22is provided at the bottom side of a shaft support 21 bearing a splitroll 20. In this structure, the tensile load applied to the split roll20 does not influence the load sensor 22 so that the peak load can bereduced. However, since the strip flatness measuring device should playits intrinsic functions as a looper before it detects the load appliedto the hot rolled strip S along the width thereof, the looperexcessively moves up and down when uneveness in mass between theneighboring stands is present due to the great difference in relativespeeds between the stands. In this case, the looper collides with anupper or lower damper so that strong impact is applied to the stripflatness measuring device, resulting in reduced life span of the loadsensor 22.

In this connection, a stopper 23 is provided at the strip flatnessmeasuring device to prevent the load sensor 22 from being applied withan over-load.

However, when the maximum load is applied to the load sensor 22, thecompressed displacement is too small to make sufficient distance forpreventing the load sensor 22 from being applied with the over-load.Thus, the mechanical means of protecting the load sensor 22 based on thestopper 23 has a limit in application in that whenever the devicesuffers slight deformation, the stopper 23 should be controlled eachtime.

Furthermore, the strip flatness measuring devices shown in FIGS. 2 and 3are interposed between the rolling stands, and the temperature of thehot rolled strips S amounts to 800 to 1200° C. In these conditions, theload sensor extremely sensitive to heat should be protected from theheat in a stable manner. If not, errors in meaurement are inevitablyfollowed by.

For that reason, a cooling nozzle 24 is provided at the strip flatnessmeasuring device to spray cooling water to the load sensor 22. However,in case the spraying of the cooling water becomes poor due to breakageor alien materials, there is a problem in that the preparation for sucha case is absent.

Furthermore, the hot rolled strips are differentiated in the loaddistribution depending upon their shapes. Therefore, when the stripflatness measuring device is used for a long time, the plural numbers ofsplit rolls 10 and 20 are rubbed in a different manner so that theybecome differentiated in horizontal height, and errors in detection withrespect to the load applied thereto are made.

In order to solve such a problem, the strip measuring device shown inFIG. 2 is provided with a height control bolt 13 for controlling thetangent-movement thereof around a rotation shaft 14, and the stripmeasuring device shown in FIG. 3 with a wedge-shaped control member 25for controlling the tangent-movement.

However, in such a case, as shown in FIG. 4A, deviation in rubbing dRbetween the split rolls 10 and 20 is made. Even though such a deviationin rubbing is controlled, as shown in FIG. 4B, deviance in controllingdR′ is present so that the load sensors 12 and 22 for detecting the loadapplied to the hot rolled strip S incorrectly detect such a load whilemaking serious errors in the flatness detection signal. That is, in theone-directional control technique, the horizontal height of themeasuring device cannot be controlled in a correct manner.

Meanwhile, in case the rubbed split rolls should be repaired or replacedby a new one, long repair or replacement time is required, loweringproductivity.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a strip flatnessmeasuring device which can protect a load sensor from the externalfactors, and control the relative heights between split rolls whilesecuring precesion in measurement.

This and other objects may be achieved by a strip flatness measuringdevice including a looper with a plurality of split rolls. The splitrolls are assembled in a bracket such that each split roll can beseparated from the bracket. A normal-movement control unit for movingthe split rolls in the normal direction, a tangent-movement control unitfor moving the split rolls in the tanget direction are provided at aside of the bracket. A support is movably connected to thetanget-movement control unit, and an impact absorption unit is installedat the support. A sensor cap is installed at a side of the support whilepressurizing a load sensor. A pre-pressure application unit is providedbetween the support and a base of the looper to previously compressesthe sensor cap against the load sensor, thereby preventing the loadsensor from being released from the sensor cap.

In the above structure, even though deviation in rubbing occurs at thesplit rolls, the normal-movement control unit and the tangent-movementcontrol units can precisely control the relative heights between thesplit rolls.

Furthermore, the load sensor is protected from the external impacts byway of the impact absorption unit and the pre-pressure application unitso that it can detect load distribution in a stable manner. The loadsensor is also protected from the heat through mounting a heat-shieldingring around the load sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or the similar components, wherein:

FIG. 1 is a perspective view of a rolling mill with a usual stripflatness measuring device;

FIG. 2 is a side view of a contact-type strip flatness measuring deviceaccording to a prior art;

FIG. 3 is a side view of a contact-type strip flatness measuring deviceaccording to another prior art;

FIGS. 4A and 4B illustrate the technique of compensating deviation inrubbing occurred at split rolls in the contact-type strip flatnessmeasuring devices shown in FIGS. 2 and 3;

FIG. 5 is a cross sectional view of a contact-type strip flatnessmeasuring device with a load sensor according to a preferred embodimentof the present invention;

FIGS. 6A and 6B are amplified sectional views of the load sensor shownin FIG. 5; and

FIGS. 7A and 7B illustrate the technique of compensating deviation inrubbing occurred at split rolls in the contact-type strip flatnessmeasuring device shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained with referenceto the accompanying drawings.

The strip flatness measuring device according to the present inventionis provided at a looper 30 between the rolling mills A and B shown inFIG. 1. The looper 30 gives tension to the hot rolled strip S whilerotating by 90 degree or less in the clockwise or anti-clockwisedirection with respect to a rotation shaft 31. Looper rolls 33 are fixedat the end portion of the looper 30 such that they directly contact thehot rolled strip S. The looper rolls are segmented by two external dummyrolls, and three measuring rolls disposed between the dummy rolls tomeasure the load applied to the hot rolled strip S. The three measuringrolls will be hereinafter referred to as the “split rolls” 35.

FIG. 5 is a cross sectional view of a contact-type strip flatnessmeasuring device according to a preferred embodiment of the presentinvention.

As shown in FIG. 5, the contact-type strip flatness measuring deviceroughly includes an impact absorption unit 40 for absorbing the impactapplied to a load sensor 37, a pre-pressure application unit 50 forapplying pressure to a sensor cap 46, a tangent-movement control unit 60for moving the split rolls 35 up and down, a normal-movement controlunit 70 for moving the split rolls 35 back and forth, and a split rollfixation unit 80 for fixing the split rolls 35.

The impact absorption unit 40 is installed at an inner groove of asupport 42 that rotates around a support shaft 41. A cylindrical-shapedrubber pad 43 is fixed to the inner groove of the support 42 using bolts45 via washers 44. The washers 44 have protrusions holding the sensorcap 46. The load sensor 37 for measuring the load applied to the splitrolls 35 is fixed to a sensor block 47 that is in turn fixed to a base39 with a cylindrical shape.

A heat-shielding ring 48 is externally screw-coupled to the sensor block47 to protect the load sensor 37 from the heat at the hot rollingtemperature of 800-1200° C. The heat-shielding ring 48 protects the loadsensor 37 through filling up the gap between the sensor block 47 and thesensor cap 46. In addition, a usual cooler may be selectively providedat the strip flatness measuring device to cool it through sprayingcooling water thereto.

A pre-pressure application unit 50 has a role of defining the rotationangle of the support 42 at a predetermined degree. The pre-pressureapplication unit 50 includes a bolt 51 coupling the end portion of thesupport 42 with the end portion of the base 39, a spherical nut 52fixing the bolt 51 to the base 39, and a disk spring 54 inserted betweenthe support 42 and a head 53 of the bolt 51. A spherical groove 55 isformed at the side of the support 42 contacting the disk spring 54. Astopper 56 is coupled to the bolt head 53 to control the rotation angleof the support 42.

A tangent-movement control unit 60 turns a bracket 71 fixing the shaftof the split rolls 35 around a bracket shaft 72 up and down. Thetangent-movement control unit 60 includes a left clevis 61 rotatablycoupled to the bracket 71, a right clevis 62 rotatably coupled to thesupport 42, and a bidirectional control bolt 63. In this structure, whenthe control bolt 63 is locked or released, the left and right devises 61and 62 become closer to each other, or distant from each other.

The normal-movement control unit 70 has a role of moving the bracket 71fixing the shaft of the split rolls 35 left and right. Thenormal-movement control unit 70 includes a slide base 74 fixed to thebody of the split rolls 35, a bracket slide 75 coupled to the bracket71, and a control bolt 76 for controlling the movement range of thebracket slide 75 left and right. The bracket 71, and the bracket slide75 are rotatably fixed around a bracket shaft 72 such that they movetogether. That is, when the bracket slide 75 moves left and right, thebracket 71 moves left and right. Whereas, when the bracket 71 isrotated, the bracket slide 75 does not rotate together.

The split roll fixture 80 has a role of making the split rolls 35 to beeasily locked or released. The split roll fixture 80 couples twoseparate split roll fixing plates 81 with a bracket fixing plate 83 viafixation bolts 82.

In operation, when a hot rolled strip S passes over the split rolls 35,the load applied to the split rolls 35 compresses the split rolls 35.Such a compression power is transmitted to the load sensor 37 via thebracket 71, the tanget-movement control unit 60, and the support 42.

The plural numbers of split rolls 35 can be easily locked or releasedvia the corresponding fixation bolts 82. Therefore, in case one of thesplit rolls 35 needs to be repaired, it can be instantly replaced by anew one.

When uneveness in mass between the rolling stands A and B occurs duringthe hot rolling process, the looper 30 moves up or down around the shaft31. In case the looper 30 excessively moves down, it collides with thelower damper while applying impact to the strip flatness measuringdevice. In this situation, the load sensor 37 suffers momentary impact.

At this time, the impact absorption unit 40 absorbs the impact appliedto the strip flatness measuring device. Therefore, the load sensor 37can correctly measure the rolling reduction ratio of the hot rolledstrip S transmitted up to the sensor cap 46.

Meanwhile, when the looper 30 excessively moves up, and collides withthe upper damper, as shown in FIG. 6A, the load sensor 37 is releasedfrom the sensor cap 46. When such a situation is repeated, the lock andrelease of the load sensor 37 into and from the sensor cap 46 arerepeated. In this case, the load sensor 37 suffers repeated momentaryimpacts while being reduced in life span.

The pre-pressure application unit 50 solves such a problem. Thepre-pressure application unit 50 previously compresses the support 42against the base 39, thereby preventing the load sensor 37 from beingreleased from the sensor cap 46 due to the impact applied to the looper30. Therefore, even though a momentary impact is applied to the support42, the load sensor 37 can correctly measure the applied load withoutbeing released from the sensor cap 46.

The hot rolled strip S passes over the looper 30 usually at thetemperature range of 800-1200° C. and hence, the thermal-sensitive loadsensor 37 is liable to be reduced in life span. In this connection, theheat-shilding ring 48 is disposed between the support 42 and the sensorblock 47 to shield the heat directly applied to the load sensor 37. Theheat-shilding ring 48 has a double structure while bearing a role ofprotecting the load sensor 37 from the heat as well as a role offunctioning as a variable stopper.

The split rolls 35 suffers rubbing due to friction against the hotrolled strip S. Therefore, it is required that the height between thesplit rolls 35 should be periodically controlled in a correct manner.

The tangent-movement control unit 60 controls the relative heightsbetween the split rolls 35, and the normal-movement control unit 70controls the left and right distance between the split rolls 35.

As shown in FIG. 7A, in case deviation in rubbing between the split roll35 bearing higher rubbing ratio and the split roll 35 bearing lowerrubbing ratio is present, as shown in FIG. 7B, the surface of the splitroll 35 is controlled to move in the tanget direction using thebidirectional control bolt 63 of the tangent-movement control unit 60,and to move in the normal direction using the control bolt 76 of thenormal-movement control unit 70. When the bidirectional control bolt 63is controlled, the surface of the split roll 35 moves to the C1 pointshown in FIG. 7B. In contrast, when the control bolt 76 is controlled,the surface of the split roll 35 moves to the C3 point. In case thesurface point of the split roll is controlled only with thebidirectional control bolt 63, the maximum control point becomes to bethe C2 point Accordingly, in order to control both surface points of therubbed split roll 35′ and the non-rubbed split roll 35, thetangent-movement control unit 60 and the normal-movement control unit 70should be used together.

Meanwhile, when the sensor cap 46 returns to its initial state, the loadsensor 37 senses the shape change of the hot rolled strip S in the upperdirection, thereby correctly measuring the flatness of the hot rolledstrip S.

The flatness of hot rolled strips S was measured through detectingcorrect distribution of the load applied to each split roll 35 andmaking feedback the detected values to the strip flatness controlsystem. The results are given in Tables 1 and 2.

TABLE 1 (Comparison in flatness of strips with a width of 900-1100 mm)Note Total numbers of collected Top (%) Middle (%) Tail (%) stripsBefore After Before After Before After before/after control controlcontrol control control control control 25.1 47.2 24.9 57.4 19.9 55.0382/322

TABLE 2 (Comparison in flatness of strips with a width of 1100-1350 mm)Note Total numbers of collected Top (%) Middle (%) Tail (%) stripsBefore After Before After Before After before/after control controlcontrol control control control control 78.0 96 4 77.0 93.9 67.8 91.9469/591

As indicated in Tables 1 and 2, the hot rolled strips that werecontrolled based on the inventive strip flatness measuring deviceexhibited evenness in flatness over the entire length thereof.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

What is claimed is:
 1. A strip flatness measuring device for measuring aflatness of a hot rolled strip based on a contact load of the hot rolledstrip applied to split rolls of a looper in the hot rolling process, thestrip flatness measuring device comprising: a tanget-movement controlunit for controlling surface points of the split rolls while moving thesplit rolls up and down; an impact absorption unit for preventing a loadsensor from suffering the impact applied to the split rolls; and apre-pressure application unit for pressurizing a support bearing asensor cap against a base holding the load sensor at a predeterminedpressure while coupling the base with the support, the base being fixedto the looper, the support being capable of rotating around a fixationshaft.
 2. The strip flatness measuring device of claim 1 wherein thetangent-movement control unit comprises a bracket, a left clevis rotablycoupled to the bracket, a right clevis rotatably coupled to the support,and a bidirectional control bolt screw-coupled to the left and rightdevises at bidirectionally screwed portions thereof.
 3. The stripflatness measuring device of claim 1 wherein the impact absorption unitcomprises an impact absorption member inserted into an inner groove ofthe support, bolts fixing the impact absorption member to the supportvia washers, and a sensor cap held by the washers.
 4. The strip flatnessmeasuring device of claim 1 wherein the pre-pressure application unitcomprises a bolt coupling an end portion of the support with an endportion of the base, a spherical nut fixing the bolt to the base, and adisk spring disposed between a head of the bolt and the support.
 5. Thestrip flatness measuring device of claim 4 wherein a spherical groove isformed at a side of the support contacting the disk spring, and astopper is coupled to the head of the bolt.
 6. The strip flatnessmeasuring device of claim 1 further comprising a normal-movement controlunit for controlling surface points of the split rolls while moving thesplit rolls left and right.
 7. The strip flatness measuring device ofclaim 6 wherein the normal-movement control unit comprises a slide basefixed to a body of the looper, a bracket slide coupled to the bracket,and a control bolt controlling the movement range of the bracket slidein the left and right directions.
 8. The strip flatness measuring deviceof claim 1 further comprising a heat-shielding unit for shielding theheat applied to the load sensor from the hot rolled strip.
 9. The stripflatness measuring device of claim 8 wherein the heat-shielding unit isformed with a heat-shielding ring, the heat-shielding ring beingexternally coupled to a sensor block, the sensor block being fixed tothe base while bearing the load sensor, the heat-shielding ring fillingup the gap between the sensor cap and the sensor block.
 10. The stripflatness measuring device of claim 1 further comprising a split rollfixture, the split roll fixture having a plurality of separate splitroll fixing plates, a bracket fixing plate, and fixation bolts couplingthe separate split roll fixing plates with the bracket fixing plate. 11.The strip flatness measuring device of claim 2 wherein the pre-pressureapplication unit comprises a bolt coupling an end portion of the supportwith an end portion of the base, a spherical nut fixing the bolt to thebase, and a disk spring disposed between a head of the bolt and thesupport.
 12. The strip flatness measuring device of claim 11 wherein aspherical groove is formed at a side of the support contacting the diskspring, and a stopper is coupled to the head of the bolt.
 13. The stripflatness measuring device of claim 3 wherein the pre-pressureapplication unit comprises a bolt coupling an end portion of the supportwith an end portion of the base, a spherical nut fixing the bolt to thebase, and a disk spring disposed between a head of the bolt and thesupport.
 14. The strip flatness measuring device of claim 13 wherein aspherical groove is formed at a side of the support contacting the diskspring, and a stopper is coupled to the head of the bolt.